Glow discharge starter switch

ABSTRACT

The invention relates to a glow discharge starter switch which is provided with an envelope of synthetic material. The invention provides a simple safety device in which the electrode path is short-circuited if too much heat is evolved in the glow discharge starter switch by means of a short-circuit device provided between the discharge tube and the synthetic material envelope. According to the invention the risk of fire of this glow discharge starter switch including the synthetic material envelope is substantially nil.

United States Patent [191 de Graaf et a1.

June 3, 1975 GLOW DISCHARGE STARTER SWITCH Inventors: Wilhelmus Polycarpus de Graaf; Jan

Man In T Veld; Adrianus Petrus Vervaart, all of Emmasingel, Eindhoven, Netherlands Assignee: U.S. Philips Corporation, New

York, NY.

Filed: July 11, 1973 Appl. No.: 378,244

Related US. Application Data Continuation of Ser. No. 237,177, March 22, 1972, abandoned.

Foreign Application Priority Data Apr. 14, 1971 Netherlands 7104999 US. Cl. 317/15; 317/16; 317/40 A;

337/404 Int. Cl. H02h 7/04 Field of Search..;..... 317/16, 40 A, 15; 337/15, 337/19, 24, 32, 404, 405, 407; 315/59, 61, 74, 75, 125

[56] References Cited UNITED STATES PATENTS 1,398,153 11/1921 Reichard 337/404 1,753,846 4/1930 Brand 337/405 1,940,176 12/1933 Marshall.. 337/405 2,379,115 6/1945 Thayer 337/24 2,527,423 10/1950 Jacobsen 337/24 2,956,210 10/1960 yatsushiro 317/15 3,294,941 12/1966 Mullen 337/140 Primary Examiner-James D. Trammell Attorney, Agent, or Firm-Frank R. Trifari [57] ABSTRACT 6 Claims, 4 Drawing Figures limit is reached.

A known glow discharge starter switch of the type mentioned above is described, for example, in U.K. Patent Specification No. 554,225. The safety device in this known starter switch consists of a second bimetal device present in the glow discharge starter switch which device short-circuits the path between the main electrodes when a large quantity of heat has evolved in the glow discharge starter switch. This second bimetal device is a complication of this known glow discharge starter switch. This applies all the more because this second bimetal device is to be proportioned in such a manner that when it is closed the current flowing therethrough must also maintain this contact closed. A further drawback of the known device is that, due to its intricacy, its reliability is rather low.

It is an object of the invention to provide a glow discharge starter switch of the kind described in the preamble which is provided with a simple and reliable safety device.

According to the invention a glow discharge starter switch provided with a discharge tube which includes a bimetal electrode and a second electrode cooperating therewith, a safety device being provided which is in a satisfactory thermal contact with the glow dischargeheated discharge path between the electrodes and which safety device produces a short circuit of the discharge path between the electrodes when a maximum temperature limit is reached is characterized in that the safety device is provided with an auxiliary member consisting of an insulation material which undergoes a permanent distortion at the maximum temperature limit, while as a result of the occurence of said permanent distortion a part of the safety device urges an electrical conductor connected to one electrode against an electrical conductor connected to the other electrode.

An advantage of this glow discharge starter switch according to the invention is that it is very simple and reliable.

The safety device may serve to present too much evolution of heat in the glow discharge starter switch itself.

However, it is alternatively feasible that the safety device is used in order to safeguard the space lighted by a low-pressure mercury vapour discharge lamp provided with preheated electrodes and ignited with this glow discharge starter switch from repeated flashes resulting from repeated ignition attempts, for example, if this mercury lamp is at the end of its life. The safety then consists of the prevention of troublesome flickering in the room where this lamp has been mounted.

As is common practice the glow discharge starter switch may be provided with an envelope consisting of, for example, metal.

In an advantageous embodiment of a glow discharge starter switch according to the invention this envelope consists of synthetic material. An advantage of this preferred embodiment is that possible danger of fire is eliminated by the safety device in the glow discharge starter switch provided with an envelope of synthetic material. The use of a synthetic material envelope in glow discharge starter switches is known per se. for example, from German Utility Model No. 1,922,109.

The safety device may be present in the discharge tube.

In a preferred embodiment of the glow discharge starter switch the safety device is present outside the discharge tube but within a possible envelope.

An advantage of this preferred embodiment is that the bimetal device within the discharge tube is not disturbed by further complications because the safety device is mechanically separated therefrom completely.

In a further preferred embodiment of the glow discharge starter switch which is provided with a capacitor arranged in parallel with the discharge path, which capacitor is present outside the discharge tube, the two electrical conductors of the safety device coincide at least partly with the two supply conductors for the capacitor.

An advantage of this preferred embodiment is that the electrical conductors have a dual function. They serve both for the supply of a current to the capacitor and for applying the current to the short-circuit device.

The connection between the two conductors may be established in different manners. In a first further preferred embodiment the auxiliary member consists of a piece of shrink tube encompassing the two conductors, the original distance between the conductors at the area of this shrink tube being so short that the shrink tube, after permanent distortion, also represents the part of the safety device which urges the two conductors against each other.

In this case there is the advantage that the shrink tube fulfils a dual function, for it is both the auxiliary member and also the part of the safety device which serve for urging the two electrical conductors against each other.

In a further preferredj embodiment the auxiliary member consists of a piece of insulation material which is present between the two conductors in which at least one of these conductors is under a mechanical pretension which attempts to movethis conductor into the direction of the other conductor.

An advantage of this embodiment is that the part of the safety device which serves for urging the conductors against each other consists of one of these conductors itself.

In a further preferred embodiment of the glow discharge starter switch according to the invention one conductor consists of a spring and a conductor part leading to one of the electrodes, the spring clamping about the last-mentioned conductor part and clamping at the other end about the auxiliary member which surrounds the other conductor.

An advantage of this embodiment is that the safety device can be provided in a very simple manner. In fact, only one insulation tube and one spring are then required. These may be provided on an existing starter.

In a further modification according to the invention the two conductors are provided with an auxiliary member consisting of an insulation material and a spring conducting electricity is clamped about these two auxiliary members.

This embodiment, too, has the advantage that it can be realized in a very simple manner with the aid of a spring and several insulation pieces. Embodiments employing an extension spring or a compression spring are possible.

The invention will be described in detail with reference to a drawing in which:

FIG. 1 shows a glow discharge starter switch and an associated capacitor, a bottom plate and an envelope in an exploded view;

FIG. 2 shows a part of the device of FIG. 1 provided with a first embodiment of the safety device according to the invention;

FIG. 3 is the same detail as shown in FIG. 2, but provided with a different safety device according to the invention; v

FIG. 4 shows the same detail as in FIG. 2, but provided with a third embodiment of the safety device.

In FIG. 1, reference numeral 1 denotes a discharge tube of a glow discharge starter switch which is provided with two bimetal electrodes 2 and 3. These electrodes are connected to two supply conductors 4 and 5, respectively. These supply conductors lead to a bottom plate 6 of synthetic material. At the other end of this bottom plate these conductors are connected to two studs denoted by 7 and 8. Furthermore two conductors 9 and 10 which lead to a capacitor 11 are connected to the conductors 4 and 5. In FIG. 1, reference numeral 12 denotes an envelope of synthetic material which when being moved in the direction of the plate 6 glides about the discharge tube 1 and the capacitor 11.

In FIG. 2, reference numeral 11 again denotes the capacitor of FIG. 1 and reference numerals 9 and 10 denote the electrical conductors. Conductor 10 is partly surrounded by a synthetic material tube 13 of insulation material, for example, polyethene of approximately 1.5 mms cross-section. Reference numeral 14 denotes a spring which consists of, for example, steel, i.e. a material satisfactorily conducting electricity. It is to be noted that the material of the spring maintains sufficient spring force at the temperature which the glow discharge starter switch may assume. This spring clamps at one end about conductor 9 and at the other end about the synthetic material tube 13.

In the glow discharge starter switch according to the combination of FIGS. 1 and 2 nothing will happen with the tube 13 and the spring 14 when little heat is evolved in the glow discharge starter switch upon the occurrence of an are between the bimetal electrodes 2 and 3. Only when arcs are repeatedly produced in a rapid succession or in case of long-lasting arcs between the electrodes 2 and 3 such an amount of heat is evolved in the discharge tube 1 that a maximum temperature limit is reached so that the material of the tube 13 will soften. Under the action of the spring force of spring 14 a short circuit of the electrode path is then brought partly surrounds the conductor 10'. In this case conductor 9' has a turn which is under amechanical pretension in such a manner that it tends to move into the direction of conductor 10'. The operation of the safety device as described with reference to FIG. 3 is broadly the same as that of FIG. 2. In fact, when too much heat is evolved in the discharge tube 1, the insulation material 13 will soften and an electrical contact will be established between the turn in the conductor 9' and the conductor 10' so that the desired short circuit of the electrode path 2, 3 of the device of FIG. 1 is obtained.

Finally FIG. 4 shows a last embodiment in which reference numerals 9" and 10 denote the two conductors which lead to capacitor 11. These two conductors are slightly bent towards each other at one area and this part is surrounded by a piece of shrink tube denoted by 15 which in the relevant case consists of teflon. This shrink tube shrinks at a temperature of from I40l 60 C such that the conductors 9" and 10" whose original distance was two mms. are urged against each other. Also in the latter case a short circuit of the electrode path of the electrodes 2 and 3 is again produced (see FIG. 1 for the electrodes). The material of the shrink tube is to have such properties that the temperature at which such a large shrinkage has occurred that the conductors contact each other is lower than the temperature at which this material softens. Teflon satisfies this property.

Consequently, all the embodiments described provide a simple safety device for a glow discharge starter switch.

What is claimed is:

1. A glow discharge starter which comprising a discharge tube including a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow discharge-heated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch, said bimetal electrode being configured to bend toward said second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit of the power supply to said starter switch when a maximum temperature limit is reached, said safety device being outside of the discharge tube and including a first and second conductor element connected to respective electrodes of said discharge tube, said first conductor having insulative material being disposed over a portion of its length as a sleeve, said insulative sleeve adapted to undergo a permanent distortion at a predetermined maximum temperature limit. and a metallic spring element mechanically and electrically coupled to said second conductor, said spring having a portion pressing under tension against said insulative sleeve, whereby said spring element cuts through said insulative sleeve to establish electrical contact between said conductors when said predetermined maximum temperature is reached, said temperature of said insulative sleeve being raised by arcing of said electrodes.

2. The starter switch of claim 1 wherein said first and second conductors are substantially parallel and said spring element bridges the two conductors, said tension being established in a direction transverse to the conductors.

3. The starter switch of claim 1 wherein said first and second conductors are substantially parallel and said spring element is an integral portion of said second conductor, said spring having a torsional tension about the axis of the first conductor.

4. The starter switch of claim 1 wherein said first and second conductors form part of a capacitor connected across the discharge tube electrodes.

5.-A glow discharge starter switch comprising a discharge tube a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow dischargeheated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch said bimetal electrode being configured to bend toward said second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit the power supply to said starter switch when a maximum temperature limit is reached, said safety device being outside of the discharge tube and including a capacitor having first and second conductor leads being connected to respective electrodes of said discharge tube, portions of said two conductor leads being in close proximity to each other, and an insulative shrink tube forming a closed loop around said portions of said conductor leads being in close proximity and adapted to undergo a permanent distortion at a predetermined maximum temperature which distortion results in a shrinking of said loop to force the two conductors into mechanical and electrical contact said tube receiving heat from arcing between said electrodes when said bimetal electrode bends toward said second electrode responsive to heat in said discharge tube.

6. A glow discharge starter switch comprising a discharge tube including a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow discharge-heated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch, said bimetal electrode being configured to bend toward second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit of said discharge path between the electrodes and maximum temperature limit is reached, said safety device being outside of the discharge tube and including a first and second conductor element connected to respective electrodes of said discharge tube, said first conductor having insulative material being disposed over a portion of itslength as a sleeve, said insulative sleeve adapted to undergo a permanent distortion at a predetermined maximum temperature limit, and means for spring biasing said second conductor against said insulating sleeve and also against said first conductor if said first conductor if said sleeve permanently distorts, the temperature of said insulating sleeves being raised by arcing of said electrodes. 

1. A glow discharge starter which comprising a discharge tube including a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow discharge-heated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch, said bimetal electrode being configured to bend toward said second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit of the power supply to said starter switch when a maximum temperature limit is reached, said safety device being outside of the discharge tube and including a first and second conductor element connected to respective electrodes of said discharge tube, said first conductor having insulative material being disposed over a portion of its length as a sleeve, said insulative sleeve adapted to undergo a permanent distortion at a predetermined maximum temperature limit, and a metallic spring element mechanically and electrically coupled to said second conductor, said spring having a portion pressing under tension against said insulative sleeve, whereby said spring element cuts through said insulative sleeve to establish electrical contact between said conductors when said predetermined maximum temperature is reached, said temperature of said insulative sleeve being raised by arcing of said electrodes.
 1. A glow discharge starter which comprising a discharge tube including a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow discharge-heated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch, said bimetal electrode being configured to bend toward said second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit of the power supply to said starter switch when a maximum temperature limit is reached, said safety device being outside of the discharge tube and including a first and second conductor element connected to respective electrodes of said discharge tube, said first conductor having insulative material being disposed over a portion of its length as a sleeve, said insulative sleeve adapted to undergo a permanent distortion at a predetermined maximum temperature limit, and a metallic spring element mechanically and electrically coupled to said second conductor, said spring having a portion pressing under tension against said insulative sleeve, whereby said spring element cuts through said insulative sleeve to establish electrical contact between said conductors when said predetermined maximum temperature is reached, said temperature of said insulative sleeve being raised by arcing of said electrodes.
 2. The starter switch of claim 1 wherein said first and second conductors are substantially parallel and said spring element bridges the two conductors, said tension being established in a direction transverse to the conductors.
 3. The starter switch of claim 1 wherein said first and second conductors are substantially parallel and said spring element is an integral portion of said second conductor, said spring having a torsional tension about the axis of the first conductor.
 4. The starter switch of claim 1 wherein said first and second conductors form part of a capacitor connected across the discharge tube electrodes.
 5. A glow discharge starter switch comprising a discharge tube a bimetal electrode and a second electrode cooperating therewith and a safety device being in close thermal relationship with the glow discharge-heated discharge path between the electrodes and responsive to heat generated in the discharge tube of said starter switch said bimetal electrode being configured to bend toward said second electrode responsive to heat in said discharge tube to allow arcing between said electrodes, said safety device produces a short circuit the power supply to said starter switch when a maximum temperature limit is reached, said safety device being outside of the discharge tube and including a capacitor having first and second cOnductor leads being connected to respective electrodes of said discharge tube, portions of said two conductor leads being in close proximity to each other, and an insulative shrink tube forming a closed loop around said portions of said conductor leads being in close proximity and adapted to undergo a permanent distortion at a predetermined maximum temperature which distortion results in a shrinking of said loop to force the two conductors into mechanical and electrical contact said tube receiving heat from arcing between said electrodes when said bimetal electrode bends toward said second electrode responsive to heat in said discharge tube. 